Electrostatic powder spraying is widely used to coat (paint) many consumer products such as appliances, tools, automobiles, etc. Much of the electrophotographic industry for producing high-quality copies and prints is based on the electrostatic deposition of charged powder. Electrostatic powder deposition is also used in a number of manufacturing processes such as abrasive coatings. Most of the applications use a non-magnetic insulative powder that is charged by either triboelectricity or gaseous ions. There are many methods and apparatus for electrostatic charging and depositing non-magnetic insulative powder on either insulative or conductive substrates. The present methods and apparatus for electrostatic powder deposition of conductive powders onto either insulative or conductive substrates have limitations. For insulative substrates, magnetic or non-magnetic conductive powder is induction charged for electrostatic deposition. Magnetic powder enables transport of the powder by permanent magnets. However, the typical processes limit the deposition to about a monolayer of powder coverage, which is less than the desired coverage for many industrial applications. For the electrostatic deposition of non-magnetic conductive powder/blend onto a conductive substrate, the inventors are not aware of literature or disclosures that describe such depositions. Thus, to date there has been no method and apparatus described in the literature that enables electrostatic multi-layer deposition of non-magnetic conductive powder onto either an insulative or conductive substrate.
It is the object of this invention to provide a method and apparatus that enables electrostatic multi-layer deposition of non-magnetic conductive powder/blend onto either insulative or conductive substrates.